A currently widely used antenna system of a mobile communication base station generally has a structure in which a plurality of radiating elements is vertically arranged which can transmit or receive an electric wave using two polarized waves which are perpendicular to each other (generally referred to as an X-shaped polarized wave). A polarized plane of the X-shaped polarized wave is basically arranged to be inclined at an angle of +45 degrees or −45 degrees with respect to the horizontal or vertical plane.
Such an antenna system commonly includes devices for remotely controlling a status of beams radiated from an antenna, for example, a Remote Azimuth Steering (RAS) device for remotely controlling azimuth steering, a Remote Azimuth Beamwidth (RAB) device for remotely controlling a beamwidth of an azimuth, and a Remote Electrical Tilt (RET) device for electronically controlling a down tilt angle. An antenna including such devices is disclosed in Korean Patent Publication No. 10-2010-0122092 first filed by Amphenol Corporation (published on Nov. 19, 2010 and entitled ‘Multi-beam Antenna with Multi-device Control Unit’; inventors Gregory Girard and Frank Soulie).
In the above description, for example, controlling the down tilt angle is used to reduce co-channel interference or to cover a region around a base station where a service is not provided. Furthermore, controlling the down tilt angle is used to minimally reduce interference between base station sectors in a region having multiple base stations due to massive telephone traffic in an urban area and to reduce interference between neighboring base stations due to antenna side-lobe. For control of the RET device, the RAS device or the RAB device described above, Antenna Interface Standards Group (AISG) v2.1.0 was recently devised, and a communication method through 3rd Generation Partnership Project (3GPP) protocol was also developed.
FIG. 1 is a block diagram illustrating an example of a main system of a base station and an antenna system for RET control of an antenna in the mobile communication base station according to the related art. According to the 3GPP or AISG standard, the RET control is largely divided into a control by a primary station and a control by a secondary station. Referring to FIG. 1, the mobile communication base station may generally include an antenna system disposed at a high place such as a building or pillar, a main system of the base station disposed on the ground, and a feeder cable connecting the antenna system and the main system, in which the primary station may correspond to the main system of the base station, and the secondary station may correspond to the antenna system.
More specifically, the primary station is a master part such as a Master Control Unit (MCU) 22 which is provided at the main system of the base station to transmit a control signal, and the secondary station is a slave part such as an RET 14 and an Antenna Line Device (ALD) modem 13 which receive the control signal to perform an operation according to the corresponding control signal.
A main body unit 21 of the base station performs basic processing operations for RF signals to be transmitted and received and transmits the RF signals through the feeder cable. The MCU 22 transmits a DC signal corresponding to operating power for driving the RET device 14 and an RS485 communication signal for control. The signals transmitted by the main body unit 21 of the base station and the MCU 22 are converted and synthesized into Direct Current (DC) signal+RF signal+On-Off Keying (OOK) signal by a bottom ALD modem 23 included in the main system of the base station. The synthesized signal is transmitted to the lower end of the antenna through the feeder cable. The top ALD modem 13 included in the antenna system filters DC signal+OOK signal out of the signal transmitted through the feeder cable as described above, and provides DC signal+OOK signal to the RET device 14 to help the RET device 14 receive a command.
At this time, the top ALD modem 13 and the RET device 14 are connected through an AISG cable, and a signal is transmitted through the AISG cable. The top ALD modem 13 and the antenna 10 are connected through a feeder cable, and an RF signal is transmitted through the feeder cable. Furthermore, the top ALD modem 13 provides the RF signal separated from DC signal+OOK signal to a first antenna 11 configured with a plurality of radiating elements for transmission and reception. Meanwhile, the antenna 10 may include a plurality of antennas, for example the first antenna 11 and a second antenna 12, configured with a plurality of transmission and reception radiating elements, and the control signal for controlling the RET device 14 may be provided through a feeder cable of one antenna, for example, the first antenna 11.
Although the RET device 14 has been exemplified as the device for receiving the control signal transmitted from the main system of the base station while being mounted to the antenna 10 and performing the operations according to the corresponding control signal, an RAS device and an RAB device may also be mounted to the antenna 10 to operate in the same manner. Furthermore, when all of the RET device, the RAS device, and the RAB device are mounted to the antenna 10, they may be connected with each other in the daisy chain manner using the AISG cable. At this time, a connection may be made such that DC signal+RS485 signal provided from the external top ALD modem 13 is primarily provided to the RET device.
In the configuration as described above, the RET device 14 is mounted within a radome forming an external appearance of the antenna 10 and is installed to be connected with the outside through an AISG connector. The top ALD modem 13 is additionally disposed as a separate device at the external lower end of the radome of the antenna 10. The top ALD modem 13 is connected with the RET device 14 through the AISG cable, and is connected with a connector, for example, a Deutsch Industrial Norms (DIN) connector formed in a lower cap of the radome of the antenna 10 through a separate feeder cable to thereby be connected with the antenna 10.
Such a configuration as described above additionally requires the separate AISG cable for signal transmission between the top ALD modem 13 and the RET device 14, the separate feeder cable for signal transmission between the top ALD modem 13 and the antenna 10, and the feeder cable having a length of several to tens of meters which is required for signal transmission from the main system of the base station to the antenna system. In addition, since the top ALD modem 13 is mounted as a separate instrument to the outside of the antenna 10, it is recognized as being considerably burdensome in terms of an installation cost, an installation space, and a weight.